Electric incandescent lamp



May 20, 1952 R. E. SMITH ELECTRIC INCANDESCENT LAMP Filed July 1, 1950Inveh lrof: Richard E. Smith by W 1? Patented May 20, 1952 ELECTRICINCANDESCENT LAMP Richard E. Smith, Shaker Heights, Ohio, assignor toGeneral Electric Company, a corporation of New York Application July 1,1950, Serial No. 171,726

6 Claims.

My invention relates in general to electric incandescent lamps, and moreparticularly to a reflector type incandescent lamp adapted to project aconcentrated light beam of high intensity.

Reflector type electric incandescent lamps of the so-called sealed beamtype described and claimed in U. S. Patent 2,148,314, D. K. Wright, andcomprising glass reflector and cover glass sections fusion-sealedtogether to form the lamp envelope and having a concentrated lightsource located at or closely adjacent the focus of the reflector arewell known in themselves and are in wide-spread use in many applicationsas, for example, in vehicle headlights, airplane landing lights,floodlights and spotlights, to mention a few. Another useful applicationis for a small portable spotlight or as a spotlight for general service,such as store lighting and display for instance, which is operable froma commercial power line and is capable of projecting an intense lightbeam over an extended distance.

It is an object of my invention, therefore, to provide a relativelyhigh-wattage electric incandescent lamp of the above-mentioned sealedbeam type which is operable from a commercial or household power sourceand which will produce a concentrated high-intensity light beam of moreor less circular cross section and of great projection distance.

Another object of my invention is to provide an electric incandescentlamp of the above character which is of rugged construction and capableof withstanding impacts or sudden jars without breakage of the filamentor distortion thereof which would result in premature filament burnoutand shortened lamp life.

Still another object of my invention is to provide an electricincandescent lamp of the above character having a filament which isconcentrated about the focal point of the focusing reflector of the lampenvelope and which is effectively supported to protect it againstphysical shock and maintain it in proper position substantially freefrom sagging during operation.

According to one aspect of the invention, a coiled-coil tungsten wirefilament of proper length and resistance for operation from an ordinarycommercial or household power line of from 110-120 volts, for instance,is divided into a plurality of separate leg portions or segments whichare disposed in a single plane and at an acute angle to one another toform either an N or Z shape or some other similar multi-segment orconcentrated planar shape, and the so-formed filament is arrangedsubstantially symmetrically about the focal point of the focusingreflector of a sealed beam type lamp such as disclosed in theabove-mentioned U. S. Patent 2,148,314, with the plane of the filamentlocated in an axial plane of the reflector axis.

According to another aspect of the invention, the above-describedN-shaped filament is firmly supported in place in the lamp envelope towithstand physical shock and maintain its initial position free fromsagging in an axial plane of the lamp reflector by having its oppositeends clamped or otherwise securely fixed to the inner ends of rigidinlead conductors and by being additionally supported intermediate itslength, at its bights or connecting loops between adjacent coil legs orsegments, by supplementary supports anchored to an insulating bridge orbridges fastened across the rigid inlead conductors.

Further objects and advantages of my invention will appear from thefollowing detailed description of species thereof and from theaccompanying drawing.

In the drawing, Fig. 1 is a sectional view of an electric incandescentlamp comprising my invention; Fig. 2 is an enlarged perspective view ofthe mount structure of the lamp shown in Fig. 1; and Fig. 3 is anenlarged fragmentary perspective view of a modification of the inventionillustrating a modified mount structure and also a modified lamp baseconstruction.

Referring to the drawing, the electric incandescent lamp according tothe invention is of the sealed beam type disclosed and claimed in theabovementioned U. S. Patent 2,148,314, D. K. Wright, and comprises asealed glass envelope or bulb l consisting of a preformed pressed glassreflector section 2 and a preformed pressed glass cover section 3fusion-sealed together at their peripheries, as indicated at 4. Thecover section 3 may be made of clear glass, or it may be stippled orotherwise rendered light-diffusing. The inner surface 5 of the reflectorsection 2 is provided with a reflecting coating 6 and is formed ofsubstantially paraboloidal shape, with a focal length of approximately 1inch or thereabouts, so as to redirect light rays from a concentratedlight source at the focus of the reflector 6 into a long beam ofsubstantially parallel rays. The reflecting coating 6 may be ofaluminum, silver or other similar light-reflective material.

Mounted on the rear outer side of the reflector section 2 at the regionof the apex or center thereof is a base structure 1 of the general typeshown and described in U. S. Patent 2,272,512, Cotman, and comprising apair of terminal con tacts 8, 6 in the form of metal straps or lugswhich are suitably fastened, as by soldering for instance, to the closednippled ends 9 of respective metal ferrules or thimbles II], It. Thecontact lugs 8, 8 are provided with screw terminals II for connectingcurrent supply wires thereto. The ferrules Ill, III are formed of asuitable metal which will readily wet and adhere to the glass of thereflector section 2 and they are provided with skirt portions I2 whichare feathered to knife edges embedded and fused in the glass of thereflector section 2 around respective openings or passageways I3 throughthe wall thereof. The envelope I is provided With an exhaust tubulationI4 communicating with the interior of the envelope through an exhaustopening I5 in the envelope wall at the apex of the reflector section 2.After exhaustion of the envelope through the tubulation I4 and, ifdesired, introduction of a suitable gas filling such as nitrogen orargon, the tubulation I4 is sealed or tipped-off as indicated at It.

Mounted within the envelope I and supported solely from the metalferrules I9, I0 is a lamp mount structure I! according to the inventionand comprising a pair of rigid wire inleads I8, I9 secured and anchoredat their outermost ends within the nipples 9 of the ferrules, as bysolder 20 as shown. The inleads I8, I9 are made of any suitablematerial, such as molybdenum, nickel or iron, which will withstand theheat to which they are subjected during lamp fabrication and operation,and they are of large enough diameter to render them relatively rigid.In the particular case illustrated, for example, the inleads I8, I9 aremade of 50 mil diameter nickelplated iron wire. From the ferrules I6,It, the inleads I8, I'9 extend in more or less parallel spaced relation(l /4 inch apart in the particular case shown) through the openings I3,I3 in the wall of the reflector section 2 and into the envelope I. Theinleads I8, I9 extend approximately parallel to and lie in a planecontaining the axis .7::c of the reflecting surface 6, and they aresubstantially symmetrically disposed on opposite sides of the said axis.Adjacent their inner ends the inleads I8, I9 are provided with inwardlyoffset end portions 2|, 22 which extend transversely of and toward theinleads I8, I9 and lie substantially in the same plane 1 as, but arespaced apart longitudinally of, the main inlead portions I8, I9. In thelamp illustrated, the inwardly offset or directed end portions 2 I, '22are formed as separate members (25 mil nickel-iron in'the case shown)which are welded or otherwise securely fastened to the main inleadportions I8, I9, but if desired they may be formed instead ascontinuations of the said main inlead portions I8, I9. At theirinnermost ends, the inleads I8, l9 are suitably connected, as byclamping or welding, to the terminal ends or extremities of an electricenergy translation element or filament 23. In the par ticular "caseshown, the innermost ends of the inlead offset portions ill, 22 areflattened and reversely bent back upon themselves to form hooks orclamps 24 within which the filament ends are clamped to thereby securelyfix the filament ends and fixedly position and rigidly support them fromthe inleads in the plane of the latter, and provide a good electricalconnection therebetween. The filament 23 comprises a fine tungsten wireof suitable design or size, i. e., length and diameter, to operate atthe particular voltage and wattage for which the lamp is designed, forexample, from a conventional commercial or household power line of fromvolts and at a wattage of say 100 to 300 watts, for instance, and it iscoiled throughout its length into small or minute minor coils and theninto larger or major coils to form a coiledcoil wire. By employing afilament in the form of a coiled-coil wire, the over-all length of thefilament body is shortened to impart ruggedness thereto and concentrateit as much as possible.

The coiled-coil filament 23 is divided into three straight leg portionsor segments 25, 26 and 21 defined by the larger or major coils of thefilament, which segments are arranged at an acute angle relative to eachother to form an N shape and are joined at the apices of the N byconnecting loops or bights 28, 29, each formed by opening up one of themajor or larger coil turns of the coiled-coil filament wire. As shown,the filament 23 is clamped to the inleads I8, I9 substantially along theaxes of the two end segments 24, 26, some of the small or minor coils ofthe single coiled end portions of the filament being crushed between thetwo sides of the inlead hooks 24 within which the filament is clamped.The angle of divergence or spread of adjacent segments of the filament23 is made sufficiently small or narrow to concentrate the filamentabout the focal point F of the reflecting surface 6, and the threesegments 25, 26, 2'! are disposed in a plane containing the axis of thereflector, and preferably in that axial plane thereof which includes theinleads, in order to present the smallest possible projecting area toobstruct the light rays reflected from the central regions of thereflecting surface 6 toward the front of the envelope. The N-shapedfilament, 23 is mounted substantially symmetrically or centered aboutthe focus F of the reflecting surface 6 with the midpoint of the centersegment 26 located at the focus F of the reflector, and with all thesegments 25, 26, 2'! extending in the general direction of the reflectoraxis and the center segment 26 crossing the reflector axis at an acuteangle (e. g., around 10 to 20 or thereabouts) varying from approximatelyonehalf to equal the angle between the center segment 26 and either endsegment 25 or 21.

. The filament 23 is additionally supported at the bights 28, 29 thereofto maintain the apices of the filament substantially in the plane of theinleads I6, I9 and hold the filament in place against sagging duringoperation, by a pair of intermediate supports, i. e., an innerintermediate support 30 and an outer intermediate support 3I The saidintermediate supports 30, 3| may be made of 10 mil diameter molybdenumwire, for instance, and they are embedded at one end in the glass rod 32of inner and outer insulative bridges or cross bars 33, 34 which arefastened across the two inleads I8, I9, in positions respectively inwardand outward 0f the filament, by support wires 35 extending from theopposite ends of the glass rods 32 and welded or otherwise secured tothe inleads to thereby rigidly tie the latter together. The intermediatefilament support wires 30, 3I extend from their respective glass rodsupports 32 toward the filament in a direction substantially parallel toand substantially in the common plane of the inleads I8, I9 and filament23. At their other or free ends the intermediate support wires 30, 3Iare bent back upon themselves to form U-shaped hooks 36, 31,respectively, which are located substantially in the common plane of theinleads I8, I9 and filament 23 and on 5 which the bights or connectingloops 28, 29 of the filament are respectively supportedto therebyposition and support the filament at its apices, free from sagging,substantially in the plane of the inleads I8, E9. The filament bights28, 29 are loosely hooked or looped over the U-shaped hooks 3B, 31 ofthe support wires 33, 3| in order to permit a limited amount of freemovement of the filament bights in the hooks longitudinally of thefilament segments during operation of the lamp to compensate for thexpansion and contraction of the filament segments, and also in order tospace the filament segments, at the apices of the filament, suificientlyfar apart to prevent contact therebetween when the lamp is subjected toa physical shock. As shown in Fig. 2, the U-shaped hooks 3B, 31 aresufficiently deep and practically parallel to one another to therebyfunction as guiding means for the apices of the filament and preventdisplacement or disengagement of the filament from the support hooks 36,31 when heated during the operation of the lamp. Preferably, theintermediate filament support wires 30, 3| are initially set to exert asufiicient pull on the apices of the filament in opposite directionslengthwise of the inleads l8, l9 so as to draw the filament segmentsmore or less taut between their points of support, thus tending to keepthe filament substantially taut and free from sagging in the planethereof during lamp operation so as to maintain the light rays in properfocus relative to the reflector. The intermediate supports 30, 3| aresufiiciently rigid to prevent permanent displacement of the filamentfrom its initial position, but the slight resiliency of these supportspermits the filament to 2,

move slightly when the lamp is subjected to a physical shock so thatthere is less danger of filament breakage than would be the case if allstrains had to be taken up by each individual segment of the filament.

The modified lamp construction illustrated in Fig. 3 differs from thatshown in Figs. 1 and 2 in and 2. "In Fig. 3, the filament 23 isconnected to and supported at its extremities by a pair of wire inleads45, 46 which extend from the ferrules l0, ID on the reflector section 2into the envelope l in spaced parallel relationto each other andsubstantially in an axial plane of the reflecting surthat, among otherthings, in place of having the lug type base 1 of Fig. 1, it is providedinstead with a base structure 38 of the side-prong type 1 shown anddescribed in U. S. patent application Serial No. 171,766-Geissbuhler etal., filed of even date herewith and assigned to the assignee of thepresent invention, and comprising a pair of terminal contacts 39, 39 inthe form of metal prongs or contact blades which are rigidly-secured andelectrically connected at one end to the closed nipple ends 9 of themetal ferrules or thimbles ll! of the lamp. The contact prongs 39 arepreferably secured to the nipple ends 9 of the ferrules 8 by beingwrapped therearound and soldered thereto, and as shown, they extendlaterally of the reflector section 2 and project outwardly from the sideof a generally cylindrical metal cup or cap 44 which is securelyfastened to the base end or apex of the reflector section to enclose theprojecting ferrules Ill and exhaust tip it located thereat. The contactprongs 39 are firmly held in spaced relation, insulated from each otherand from the metal cap 40, by an insulative face 6. One of the inleads(45) is longerthan the other, and they are both bent or turned inward attheir inner ends'to form inwardly directed end portions 41, 48 whichextend toward the reflector axis and lie in the same plane as the maininlead portions 45 and 46 but-are spaced apart longitudinally of thereflector axis by reason of the difference in lengths of the inleads.The innermost ends of the inleads 45, 46 are formed with hooks 49 withinwhich the filament extremities are clamped substantially along the axesof the two outer or end segments of the filament to thereby firmlysupport the filament in place at its extremities. As in the case Of theprevious form of the invention, the N-shaped filament 23 of Fig. 3 islikewise mounted in the same axial plane of the reflecting surface 6 asthat containing the two inleads 45, 46, and it is symmetrically disposedand centered about the focus F of the reflecting surface 6 in the samemanner as in Figs. 1 and 2. I

The filament 23 in Fig. 3 is additionally supported at the bights 28, 29thereof, to hold it in place against sagging during operation, by a pairof intermediate supports 50 and 5!, respectively. Thesaidintermediate'supports; may be made of 12 mil diameter molybdenumwire,. for instance, and they are each embedded at one end in the glassrod 52 of an insulative bridge or cross bar 53 which is similar tothebridges 33 and 34 of Figs. 1 and 2 and isfastened across the twoinleads 45, 46 by pairs of support wires 54, 54 extending from theopposite ends of the glass rod. 52 and welded or otherwise secured tothe inleads, to thereby rigidly tie the said inleads together. One ofthe intermediate filament support wires (50) is longer than the othersupport wire 5| and it extends from the glass insulator rod 52. in adirection transversely to theplane of inleads 45, 46 as indicated at 55and is then bent to extend outwardly of the reflecting surface 6 in adirection more or less parallel to or at a slight angle to the axis ofthe reflector, as indicated at 56. The free end of the support wire 50is bent inwardly toward the filament to form an inturned arm 51 formedwith a U-shaped loop or hook 58 within which the upper bight 29 of thefilament is loosely hooked to thereby position and support the filamentat its outer apex against sagging. The other or shorter support wire 5|extends from the glass insulator rod 52 in a direction outwardly of thereflector 2 and substantially parallel to the reflector axis and in theplane of the filament 23, and is likewise provided at its free end witha U-shaped loop or hook 59 within which the lower bight 28 of thefilament is loosely hooked to thereby position and support the filamentat its inner apex against sagging.

The angle of divergence or spread of adjacent segments 25, 26, and 2'!of the N-shaped filament 23 of Figs. 1 to 3 is made relatively small,for example, of the order of 20 or thereabouts. This, coupled with thecoiled-coil construction of the filament, serves to concentrate thefilament at and adjacent the focal point of the reflector 6 sufficientlyso as to produce a light beam which is of substantially circular orslightly elliptical section and free from a dark spot or area at thecenter thereof, the center filament segment 26 producing a more or lessbright spot of light at the center of the beam and the two outersegments 25 and 21 producing bright spots of light slightly to eitherside of the center spot depending on the spread of the segments. This isin marked contrast to the beam produced by a V- shaped coiled-coilfilament mounted symmetrically about the focus F of the reflector so asto lie in an axial plane of the reflector with its apex pointed outwardand located on the axis of the reflector, such a beam beingcharacterized by a darkened spot at the center of the beam due to thefact that the two diverging legs of the V filament product bright spotslocated slightly to either side of the center of the beam.

From the above description, it will be apparent that I have provided asealed beam type of lamp for operation from a power line of any suitablevoltage, such as a conventional commercial or household power line of110 to 120 volts for example, and which will operate to project aconcentrated and substantially circular light beam of high intensity fora relatively great distance. The filament is composed of a plurality ofangularly disposed coiled-coil segments or portions which concentratethe filament so as to approximate the desired point source of light foruse with the focusing reflector, and an effective supporting arrangementis provided to support the filament rigidly at its terminal extremitiesas well as at points intermediate its ends to thereby protect it againstphysical shock and maintain all portions theerof substantially in theirinitial position, free from sagging, in an axial plane of the reflectorduring all operating conditions throughout the life of the lamp.

Although preferred species of my invention have been disclosed, it willbe understood that the invention is not to be limited to the specificconstruction and arrangement of parts shown, but that they may be widelymodified within the spirit and scope of my invention as defined by theap; pended claims. 1

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric incandescent lamp comprising a sealed envelope having afocusing reflector for producing a long beam of substantially parallelrays. 2. coiled-coil filament in said envelope comprising a plurality ofindividual segments disposed in a common plane and arranged atsubstantially the same acute angle with respect to each other. a pair ofspaced rigid inlead conductors in said envelope extending substantiallyparallel to and disposed substantially in a plane containing the focalaxis of said reflector and having inwardly directed portions extendinglaterally of and toward the axis of the reflector so as to liesubstantially in said plane, said inwardly directed conductor portionsbeing spaced apart longitudinally of the reflector axis and beingconnected to the ends of said filament to rigidly support the saidfilament ends in said plane, and means for additionally supporting thefilament at the junctions between the said segments thereof to hold itsubstantially centered about the focal point of the reflector and insaid plane with its segments extending in the general direction of thereflector axis and its center segment arranged at an acute angle to theaxis of the refiector and extending through the focal point thereof,said additional supporting means maintaining the filament substantiallyin said plane under the operating conditions of the lamp whereby tomaintain the light beam from the lamp properly focused.

2. An electric incandescent lamp comprising a sealed envelope having afocusing reflector for producing a long beam of substantially parallelrays, a coiled-coil filament in said envelope comprising threeindividual segments arranged in substantially an N-shape, a pair ofspaced rigid inlead conductors in said envelope extending substantiallyparallel to and disposed substantially in a plane containing the focalaxis of said reflector and having inwardly directed portions extendinglaterally of and toward the axis of the reflector so as to liesubstantially in said plane, said inwardly directed conductor portionsbeing spaced apart longitudinally of the reflector axis and beingconnected to the ends of said filament to rigidly support the saidfilament ends in said plane, and means for additionally supporting thefilament at the junctions between the said segments thereof to hold itsubstantially centered about the focal point of the reflector and insaid plane with its segments extending in the general direction of thereflector axis and its center segment arranged at an acute angle to theaxis of the reflector and extending through the focal point thereof,said additional supporting means maintaining the filament substantiallyin said plane under the operating conditions of the lamp whereby tomaintain the light beam from the lamp properly focused.

3. An electric incandescent lamp comprising a sealed envelope having afocusing reflector for producing a long beam of substantially parallelrays, a coiled-coil filament in said envelope comprising threeindividual segments arranged in substantially an N-shape, a pair ofspaced rigid inlead conductors in said envelope extending substantiallyparallel to and disposed substantially in a plane containing the focalaxis of said reflector and having inturned inner end portions extendinglaterally of and toward the axis of the reflector so as to liesubstantially in said plane, said inturned conductor portions beingspaced apart longitudinally of the reflector axis and being connected tothe ends of said filament to rigidly support the said filament ends insaid plane, and means for additionally supporting the filament at thejunctions between the said segments thereof to hold it substantiallycentered about the focal point of the reflector and in said plane withits segments extending in the general direction of the reflector axisand its center segment arranged at an acute angle to the axis of thereflector and extending through the focal point thereof, said additionalsupporting means maintaining the filament substantially in said planeunder the operating conditions of the lamp whereby to maintain the lightbeam from the lamp properly focused.

in claim 3 wherein the additional support means for the filamentcomprises an insulative bridge member fastened across the said inleadconductors at a position inwardly of the filament and provided with apair of support wires each hav- 2,597,681 9 19 ing a hook on whichrespective junctions between the filament segments are hooked.REFERENCES CITED 6. An electric incandescent lamp as set forth in claim2 wherein the center segment of the said N-shaped filament crosses theaxis of the reflec- The following references are of record in the fileof this patent:

UNITED STATES PATENTS tor at an acute angle ranging from approximatelyone-half to equal the angle between the Numbel Name Date center segmentof the filament and an adjacent 2497567 stone 1950 2,508,063 Gross May16, 1950 segment thereof.

RICHARD E. SMITH. 10

